The instant invention relates to a device for testing the strength of metal cans. More particularly, it is concerned with an improved device for testing the buckling strength of a closed end metal can body. Quality control practices presently used in the manufacture of seamless metal cans, such as those produced by the draw and iron process, or cans wherein the side and one end are integral, require that specimen cans be periodically and randomly removed from the production line prior to filling and placed in an end buckle-testing device for the purpose of determining their respective end buckling strengths.
The buckle strengths required for various commercially acceptable can bodies depend upon the particular structure of the can involved and the product to be packaged in the can. For example, the integral end of a seamless drawn and ironed aluminum can body used to package beer may, according to present packaging standards, have to possess a minimum 88 psi end buckle strength to be acceptable commercially. Prior art machines used for making the above tests were not always easy to operate or maintain and sometimes posed safety hazards to the operator.
For example, some prior art can-testing machines would not readily accommodate cans of varying sizes or slightly uneven open ends and then tightly hold and seal the can interiors from the atmosphere during testing. Others required operators having a certain amount of strength and were susceptible to jamming. Still other types of testing equipment that have been used in the past as buckle testers have permitted the can ends and/or bodies to become so deformed during testing that they would become bound or frozen to the machine, whereby they could be extracted only with extreme difficulty and by means of special tools.
Typical can body wall and/or end testing devices representative of the prior art are illustrated in U.S. Pat. Nos. 715,324; 1,118,478; 2,696,106; 3,336,793; 3,418,845; 3,672,208; 4,027,513 and British Pat. Nos. 1,502,555 and 1,518,363, as well as the testers manufactured and sold by the Newby Precision Machinery Company of Tracy, California, and the Altek Company of Torrington, Connecticut, the latter of which used Model No. 9009 to designate the same. The tester of the first-mentioned company utilized a system of externally disposed complex clamping fingers for pressing the can body wall from the outside into contact with a sealing ring disposed on a can-receiving interior mandrel upon which the can was mounted. The tester of the Altek Company utilized an interior mandrel plug means and complex outer toggle arms for forcing a sealing ring associated with the mandrel plug means into contact with the interior wall of the can body and then maintaining said contact. Both of these latter testers, however, were not always reliable. They were difficult to operate and susceptible to jamming.
The instant development is concerned with providing a can end buckle-testing device of improved characteristics and reliable yet simplified design.